Retracts would probably work fine off pavement. Just be careful of your landings and don't bend the wires up! Like I said earlier, it is easy to stall the Nobler if you let it get too slow on landing.

Everything is so tight on this plane that it would be tough to add retracts later. But you could probably build for retracts but then rig it for the wire gear just to get started. If you are installing retracts you will need to be careful to build the plane as light as you can, cause it wants to come out on the heavy side. It is built like a tank- no lack of lumber!

JR 537 servos are plenty for the Nobler- that's what I am using with a 4.8V 800mah battery. I use a small battery to keep weight down. If I were adding retracts I would also use a mini-servo for the throttle just to cut down on weight a little more.

The flap servo is located at the middle of the wing sort of like a trainer arrangement but it is connected to a joiner wire that connects the flaps together. The plans show how to do this. Again, using two servos for the flaps would just add complexity and weight.

The new AX motor is awsome! I tested my new one on my LT-40 trainer and the plane was unlimited! Much stronger than the FX that I had on it. It is definitely going to be the right motor for the Nobler.

I don't think there is room for a Pitts muffler in the cowl. The fuse is extremely narrow which makes everything very tight. By the way the tank that is recommended in the plans will not fit. But Hayes makes one that will go right in.

I used Ultracoat on my plane. Covering is pretty straightforward- the wing tips are the only tricky part.

Keep the questions coming and I'll keep on doing my best to provide answers!